Hydrogen generator

ABSTRACT

Hydrogen generation materials are a complex hydride which generates hydrogen upon hydrolysis, and an aqueous solution comprising water for causing the hydrolysis, and an accelerator dissolved therein for accelerating a hydrogen generation reaction. A method of hydrogen generation by a hydrogen generator comprises a first step S 1  of detecting that the internal pressure of a reactor is lower than a reference pressure, and supplying the aqueous accelerator solution to the reactor; a second step S 2  of dissolving the complex hydride in the aqueous accelerator solution to cause a hydrogen generation reaction; and a third step S 3  of detecting that the internal pressure of the reactor is higher than the reference pressure, and stopping the supply of the aqueous accelerator solution, and repeats the flow from the first step S 1  to the third step S 3.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates to a hydrogen generator for efficiently supplyinghydrogen to a device requiring hydrogen, such as a fuel cell or ahydrogen engine, or a hydrogen storage container.

2. Background Art

As energy problems and environmental problems have attracted increasingattention in recent years, expectations are growing that hydrogen, whichis a fuel other than a fossil fuel, will serve as a clean-emission fuel.However, hydrogen poses problems in all aspects, such as production,storage, transportation, and technologies for utilization, and thedevelopment of a technique for handling it is an urgent task.

As a power generator utilizing hydrogen, a fuel cell and an internalcombustion engine (hereinafter referred to as a hydrogen engine) arenamed. These power generators are targeted for all business categories,including district-distributed power supplies, buildings, households,automobiles, and portable instruments. In any such cases, apredetermined amount of hydrogen needs to be supplied promptly. Theautomobiles and portable instruments, in particular, need a space forinstallation of a power generator, and require efficient supply ofgenerated power to a device which consumes electric power. Thus,hydrogen supply instruments and hydrogen generation materials arerequired to have a high hydrogen storage density, and to be capable ofgenerating hydrogen with low energy.

A method of hydrolyzing a complex hydride, called a chemical hydride,has so far been known as a method for obtaining hydrogen with lowenergy. For example, there have been known a method which comprisesdissolving lithium borohydride, sodium borohydride, lithium aluminumhydride, or sodium aluminum hydride, any of which is a type of complexhydride, in an aqueous alkaline solution, and supplying the resultingaqueous solution to a precious metal catalyst for their contact, therebycausing a hydrogen generation reaction; and a method by which water oralcohol is supplied to a complex hydride to cause a hydrogen generationreaction (see, for example, Patent Document 1).

In this case, the reactants of the hydrogen generation reaction are thecomplex hydride and water, and the catalyst has the effect of anaccelerator for accelerating the hydrogen generation reaction.

[Patent Document 1]

Japanese Unexamined Patent Publication No. 2003-206101 (pages 4 to 6,FIG. 1)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, when the complex hydride is dissolved in the aqueous alkalinesolution to cause reaction, as before, the probability of contactbetween the complex hydride and the precious metal catalyst changes overtime, posing problems such that the supply of the aqueous alkalinesolution of the complex hydride is complicated to control, control ofthe hydrogen generation reaction is difficult, and the amount ofhydrogen generation based on the total weight of the complex hydride(hereinafter referred to as the reaction efficiency) is small. This isbecause if the concentration of the aqueous solution of sodiumborohydride exceeds 12% by weight, sodium metaborate as the product ishydrated and precipitated, thus making it difficult to bring sodiumborohydride into contact with the catalyst uniformly with highefficiency.

According to the method of supplying water or alcohol to the complexhydride, on the other hand, the reaction rate is so low that it isdifficult to obtain hydrogen at a rate necessary for the powergenerator. With this method, an increase in the amount of water oralcohol supplied can accelerate the reaction rate. However, the amountof the complex hydride with respect to water or alcohol becomesextremely small. Thus, the problem arises that the amount of hydrogengeneration based on the weight of all reactants (hereinafter referred toas the hydrogen storage density) is decreased.

SUMMARY OF THE INVENTION

The present invention has been accomplished in the light of theabove-described situations. It is an object of the invention to providea hydrogen generator which permits uniform and efficient contact betweena complex hydride and a catalyst, can generate hydrogen at a requiredrate, and imparts a high reaction efficiency and a high hydrogen storagedensity.

MEANS FOR SOLVING THE PROBLEMS

A hydrogen generator according to the present invention, for attainingthe above object, is a hydrogen generator in which a reacting aqueoussolution (aqueous reagent solution), used for a hydrogen generationreaction, is supplied to a complex hydride to generate hydrogen,comprising: a supply section for supplying the reacting aqueous solutionsuch that a total weight of water contained in reacting aqueous solutionsupplied to the complex hydride is 0.2 times or more, but 3 times orless, a weight of the complex hydride.

A hydrogen generator of the present invention, for attaining the aboveobject, is a hydrogen generator in which a reacting aqueous solution,used for a hydrogen generation reaction, is supplied to a complexhydride to generate hydrogen, wherein a metal chloride is contained inthe reacting aqueous solution, and a concentration of the metal chlorideis 0.1% by weight or more, but 40% by weight or less.

By so doing, in the hydrogen generation reaction in which the complexhydride and water are reacted, the reacting aqueous solution is suppliedto the complex hydride. Thus, the reaction rate can be increased,despite a small amount of water. Moreover, uniform contact of thereacting aqueous solution with the complex hydride can be made.

A hydrogen generator according to the present invention, for attainingthe above object, is a hydrogen generator in which a reacting aqueoussolution, used for a hydrogen generation reaction, is supplied to acomplex hydride to generate hydrogen, wherein a pH of the reactingaqueous solution is 1 or higher, but 3 or lower. Moreover, the pH of thereacting aqueous solution is preferably 1.4 or higher, but 2 or lower.

A hydrogen generator according to another aspect of the presentinvention is one wherein the total weight of the water in the reactingaqueous solution is 1.0 times or more, but 3 times or less.

By so doing, in the hydrogen generation reaction in which the complexhydride and water are reacted, the reacting aqueous solution can besupplied, together with the accelerator, to the complex hydride. As aresult, when the complex hydride and water are reacted, the acceleratoris always supplied to the reaction section. Thus, the reaction rate canbe increased, despite a small amount of water. Moreover, the probabilityof contact between the complex hydride and the accelerator does notchange, and uniform contact can be made. Consequently, the water-solubleaccelerator is uniformly dispersed in the aqueous solution, thus makingit possible to achieve a constant probability of contact between thecomplex hydride and the accelerator.

Furthermore, 9% by weight of hydrogen is obtained based on the weight ofthe reacting aqueous solution and the complex hydride, and a highhydrogen storage density is achieved. Under highly acidic conditions,the volume or weight of the aqueous solution of the acid is great.However, the reaction efficiency is improved, with the result that itbecomes possible to increase the hydrogen storage density per volume orper weight.

A hydrogen generator according to another aspect of the presentinvention is one wherein a metal chloride is contained in the reactingaqueous solution, and a concentration of the metal chloride is 0.1% byweight or more, but 25% by weight or less. Preferably, the concentrationof the metal chloride is 1% by weight or more, but 15% by weight orless.

A hydrogen generator according to another aspect of the presentinvention is one wherein a pH of the reacting aqueous solution is 1 orhigher, but 3 or lower.

A hydrogen generator according to another aspect of the presentinvention is one wherein the concentration of the metal chloride is 0.1%by weight or more, but 25% by weight or less.

A hydrogen generator according to another aspect of the presentinvention is one wherein a metal chloride is contained in the reactingaqueous solution, and a concentration of the metal chloride is 0.1% byweight or more, but 25% by weight or less.

A hydrogen generator according to another aspect of the presentinvention is one wherein the complex hydride is a boron hydride salt.

A hydrogen generator according to another aspect of the presentinvention is one wherein a carboxylic acid is contained in the reactingaqueous solution.

The carboxylic acid is preferably at least one of those included in agroup consisting of citric acid, malic acid, succinic acid, tartaricacid, malonic acid, oxalic acid, and maleic acid. These acids are notvolatile, and can prepare a stable aqueous acid solution.

A hydrogen generator according to another aspect of the presentinvention is one wherein an anti-foaming agent is contained in at leastone of the reacting aqueous solution and the complex hydride. Thehydrogen generator according to a further aspect is characterized inthat a complex hydride anti-foaming agent is contained.

Because of this feature, contact between the complex hydride and thereacting aqueous solution is easily made. That is, when the reactingaqueous solution is supplied to the complex hydride, particularly in thecase of a high ratio of the boron hydride salt, the amount of waterdecreases immediately after the reaction, and the viscosity of theproduct is very high. As a result, foams engulfing hydrogen, the complexhydride, and the product occur in large amounts, but are apt todisappear because of the effect of the anti-foaming agent. Consequently,it becomes possible to suppress the inhibition, due to the foams, ofcontact between the reacting aqueous solution and the complex hydride,and curtail decreases in the reaction rate and the reaction efficiency.Since the outflow of foams can be suppressed by anti-foaming, moreover,the volume of the reactor storing the complex hydride can be reduced toincrease the hydrogen storage density.

A hydrogen generator according to another aspect of the presentinvention is one wherein the reacting aqueous solution supplied to thecomplex hydride is brought into contact with a solid accelerator for ahydrogen generation reaction.

A hydrogen generator according to another aspect of the presentinvention is one wherein the solid accelerator contains the same type ofaccelerator as the accelerator contained in the reacting aqueoussolution.

Even when the reacting aqueous solution and the complex hydride aremixed, not all of the reactants react immediately. Thus, a mixed aqueoussolution comprising a mixture of the reactants and the resulting productis first formed. Since this aqueous solution contains the complexhydride, it causes a hydrogen generation reaction. The reaction rate isslowed compared with that immediately after supply of the reactingaqueous solution. Hence, contact with a solid accelerator held in asolid form can result in an increased reaction rate. It does not matterwhether the type of the accelerator in the reacting aqueous solution,and the type of the solid accelerator are identical or different.

A hydrogen generator according to another aspect of the presentinvention is one wherein the solid accelerator is a precious metal or ahydrogen absorbing alloy.

Iridium, osmium, palladium, ruthenium, rhodium, platinum, and gold canbe used as the precious metal. The precious metal and the hydrogenabsorbing alloy show a catalytic action involved in the hydrolysisreaction of the complex hydride. Thus, contact of the precious metal orthe hydrogen absorbing alloy with the mixed aqueous solution canincrease the reaction rate. Such a meta- or alloy-based catalyst doesnot dissolve in the mixed solution. Thus, the catalyst shows a constantcatalytic effect regardless of the liquid nature of the mixed solution,and can stably generate hydrogen.

A hydrogen generator according to another aspect of the presentinvention is one wherein the complex hydride and the solid acceleratorare disposed in a mixed form.

A hydrogen generator according to another aspect of the presentinvention is one wherein the reacting aqueous solution is stored in anaqueous solution storage section, the complex hydride is stored in ahydrogen supply section comprising a reaction section for causing ahydrogen reaction, a supply pipe leading to an external device isconnected to the hydrogen supply section, and the reacting aqueoussolution from the aqueous solution storage section is supplied to thecomplex hydride by the hydrogen supply section.

By so doing, the initiation and termination of the hydrogen generationreaction can be controlled by supplying the reacting aqueous solutionand stopping the supply of the reacting aqueous solution. Thisfacilitates reaction control.

A hydrogen generator according to another aspect of the presentinvention is one wherein the hydrogen supply section has a function ofperforming a first step in which a value obtained by adding a pressurelost in the supply pipe to a set hydrogen pressure in the externaldevice is taken as a reference pressure, and when an internal pressureof the external device is lower than the set hydrogen pressure, and whenan internal pressure of the reaction section is lower than the referencepressure, the reacting aqueous solution is supplied to the complexhydride; a function of performing a second step in which hydrogen isgenerated, with the complex hydride being dissolved in the reactingaqueous solution; and a function of performing a third step in whichwhen a pressure of hydrogen supply from the reaction section to theexternal device is higher than the reference pressure, the supply of thereacting aqueous solution is stopped, and the first step to the thirdstep are performed repeatedly sequentially in the hydrogen supplysection.

Because of these features, when hydrogen is consumed in the externaldevice, hydrogen can be generated and supplied in synchronization withthe rate of consumption. The hydrogen generation reaction occurs uponsupply of the reacting aqueous solution to the complex hydride. Theamount of hydrogen generated during this reaction is determined by theamount of water contained in the reacting aqueous solution. Thus, whenthe reacting aqueous solution is supplied, or its supply is stopped, inaccordance with the difference between the internal pressure of thereaction section and the reference pressure, the amount of hydrogennecessary for its consumption in the external device is suppliedintermittently, so that the amount of hydrogen supply can be controlledeasily.

A hydrogen generator according to another aspect of the presentinvention is one wherein after supplying the reacting aqueous solutionto the complex hydride, the hydrogen supply section supplies thereacting aqueous solution such that a rate of hydrogen generationexceeds a rate of hydrogen consumption in the external device at leastonce.

By so doing, the internal pressure of the reaction section and theexternal device can be increased, and the flow of a series of steps,ranging from the first step to the third step, can be performedrepeatedly. The amount of supply of the reacting aqueous solution isdetermined by the status of the increase in the internal pressure. Thus,if the hydrogen generation reaction occurs promptly, the amount ofsupply is small. If the complex hydride is covered with the product todelay contact between the reacting aqueous solution and the complexhydride, or if the temperature of the reaction section is low, the rateof the hydrogen generation reaction lowers, thus making it necessary toincrease the amount of supply of the reacting aqueous solution, therebyraising the speed of hydrogen generation.

A hydrogen generator according to another aspect of the presentinvention is one wherein the hydrogen supply section supplies thereaction aqueous solution such that the internal pressure of thereaction section becomes higher than the reference pressure by 0.3 kPato 300 kPa.

Because of this feature, the internal pressure of the reaction sectionis not excessive, so that operation can be performed safely.

A hydrogen generator according to another aspect of the presentinvention is one wherein an amount of supply of reacting aqueoussolution in the first step is set in the hydrogen supply section suchthat a theoretical hydrogen pressure obtained by dividing astoichiometric amount of generation of hydrogen, which is generated uponreaction between the water contained in the reacting aqueous solutionand the complex hydride, by a capacity of the hydrogen supply section is5 kPa to 300 kPa.

By so doing, an excessive rise in the pressure inside the hydrogensupply section can be suppressed, and a safe operation can be performed.

A hydrogen generator according to another aspect of the presentinvention is one wherein the external device is a fuel cell, and asupply pipe is connected to a negative electrode chamber of the fuelcell.

A hydrogen generator according to another aspect of the presentinvention is one wherein a set hydrogen pressure of the fuel cellconnected is not lower than a pressure of a positive electrode chamberof the fuel cell, but is not higher than a pressure which is higher thanthe pressure of the positive electrode chamber by 0.3 MPa.

Because of this feature, the difference between the pressures imposed bythe positive and negative electrode chambers on an electrolyte presentbetween the positive and negative electrode chambers is within the rangeof 0.305 MPa to 0.6 MPa at the greatest. If a pressure corresponding tothe amount of hydrogen consumed by the fuel cell is subtracted from thispressure difference, stress imposed on the electrolyte can be reduced toless than the durability of the electrolyte.

A hydrogen generator according to another aspect of the presentinvention is one having a conduit connecting the aqueous solutionstorage section and the reaction section, and a check valve as a controldevice provided in the conduit and opening and closing under adifferential pressure between the aqueous solution storage section andthe reaction solution, the check valve opening when the internalpressure of the reaction section becomes lower than the referencepressure, to permit flow of the reacting aqueous solution toward thereaction section, and the check valve closing when the internal pressureof the reaction section becomes higher than the reference pressure, tostop the flow of the reacting aqueous solution toward the reactionsection.

Because of the above features, there is no need for an electrical methodof detection and control, which comprises converting pressure into anelectrical signal with the use of a pressure sensor, and supplying thereacting aqueous solution. In other words, according to the check valve,a change in force associated with the difference between the internalpressure of the reaction section and the reference pressure is detectedby the valve body of the check valve, whereby the valve can be openedand closed automatically. In this manner, the reacting aqueous solutioncan be supplied, and its supply can be stopped, in accordance with thedifference between the reference pressure exerted on the reactingaqueous solution and the internal pressure of the reaction section.

A hydrogen generator according to another aspect of the presentinvention is one having a conduit connecting the aqueous solutionstorage section and the reaction solution, and a regulator as a controldevice provided in the conduit, the regulator opening when the internalpressure of the reaction section becomes lower than the referencepressure, to permit flow of the reacting aqueous solution toward thereaction section, and the regulator closing when the internal pressureof the reaction section becomes higher than the reference pressure, tostop the flow of the reacting aqueous solution toward the reactionsection.

A fuel cell apparatus can be constructed by connecting the hydrogensupply section of the hydrogen generator to a negative electrode chamberof a fuel cell, the negative electrode chamber being supplied withhydrogen generated. According to this feature, it becomes possible toprovide a fuel cell apparatus equipped with a hydrogen generator whichcan increase the rate of hydrogen generation, which can heighten thereaction efficiency and the hydrogen storage density, and which is easyto control.

EFFECTS OF THE INVENTION

In the present invention, the reacting aqueous solution is supplied tothe complex hydride, whereby water as the reactant for the hydrogengeneration reaction and the accelerator for raising the reaction ratecan be simultaneously supplied to the complex hydride. As a result, itbecomes possible to provide a hydrogen generator which enables theaccelerator and the complex hydride to be brought into contact uniformlyand efficiently, which can increase the rate of hydrogen generation,which can render the reaction efficiency and the hydrogen storagedensity high, and which is easy to control.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

A process flow chart of a hydrogen generation method by a hydrogengenerator according to an embodiment of the present invention.

FIG. 2

A schematic configuration drawing of a fuel cell apparatus equipped witha hydrogen generator according to the embodiment of the presentinvention.

FIG. 3

A graph showing changes in the internal pressure of a hydrogen supplyinstrument and changes over time in the output voltage of a fuel cellwhen the hydrogen supply instrument and the fuel cell were operatedusing the hydrogen generator according to the present invention.

FIG. 4

A graph showing the malic acid concentration dependence of the reactionefficiency when sodium borohydride was dissolved in an aqueous solutionof malic acid.

FIG. 5

A graph showing the sodium borohydride concentration dependence of thereaction efficiency.

FIG. 6

A graph showing the dependence of the reaction efficiency on the pH ofthe malic acid concentration.

FIG. 7

A view, in tabular form, illustrating aqueous accelerator solutionswhich are reacting aqueous solutions, and combinations of an acceleratorand a solid accelerator.

FIG. 8

A graph showing the dependence of the reaction efficiency on theconcentration of nickel chloride.

FIG. 9

A graph showing changes over time in the pressure of hydrogen generatedwhen a solid catalyst is not accommodated.

FIG. 10

A graph showing changes over time in the pressure of hydrogen generatedwhen the solid catalyst is accommodated.

FIG. 11

A schematic configuration drawing of a hydrogen generator according to afirst embodiment of the present invention.

FIG. 12

A schematic configuration drawing of a hydrogen generator according to asecond embodiment of the present invention.

FIG. 13

A schematic configuration drawing of a hydrogen generator according to athird embodiment of the present invention.

FIG. 14

A schematic configuration drawing of a fuel cell apparatus according tothe first embodiment of the present invention.

FIG. 15

A schematic configuration drawing of a fuel cell apparatus according tothe second embodiment of the present invention.

FIG. 16

A schematic configuration drawing of a hydrogen generator according to afourth embodiment of the present invention.

FIG. 17

A schematic configuration drawing of a hydrogen generator according to afifth embodiment of the present invention.

FIG. 18

A schematic configuration drawing of a hydrogen generator according to asixth embodiment of the present invention.

FIG. 19

A schematic configuration drawing of a fuel cell apparatus according toa third embodiment of the present invention.

FIG. 20

A schematic configuration drawing of a fuel cell apparatus according toa fourth embodiment of the present invention.

FIG. 21

A schematic configuration drawing of a fuel cell apparatus according toa fifth embodiment of the present invention.

DESCRIPTION OF THE NUMERALS AND SYMBOLS

-   -   1 Reaction section    -   2 Aqueous solution storage section    -   3 Connecting pipe    -   4 Check valve    -   5 Air inlet    -   6 Anode chamber of fuel cell    -   7 Hydrogen supply pipe    -   S1 First step    -   S2 Second step    -   S3 Third step

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will now be described in detailbased on the accompanying drawings.

FIG. 1 shows the process flow of a hydrogen generation method by ahydrogen generator according to an embodiment of the present invention.

As shown in the drawing, the first step S1 is the step of detecting thatthe internal pressure of a reactor is lower than a reference pressure,and supplying an aqueous accelerator solution as a reacting aqueoussolution to the reactor. The second step S2 is the step of dissolving acomplex hydride in the aqueous accelerator solution to cause a hydrogengeneration reaction. The third step S3 is the step of detecting that theinternal pressure of the reactor is higher than the reference pressure,and stopping the supply of the aqueous accelerator solution. Byrepeating the flow from the first step S1 to the third step S3, hydrogencan continue to be supplied. In the present embodiment, malic acid wasused as the accelerator of the aqueous accelerator solution, and sodiumborohydride was used as the complex hydride.

FIG. 2 shows the schematic configuration of a fuel cell apparatusequipped with a hydrogen generator according to the embodiment of thepresent invention.

As shown in the drawing, a hydrogen supply instrument comprises ahydrogen reaction section (reaction section) 1 which accommodates sodiumborohydride as a complex hydride and causes a hydrogen generationreaction, and an aqueous solution storage section 2 which stores anaqueous solution of malic acid as an aqueous accelerator solution whichis a reacting aqueous solution. The reaction section 1 and the aqueoussolution storage section 2 are connected by a connecting pipe 3. Theconnecting pipe 3 is provided with a check valve 4 as a valve, and theaqueous solution storage section 2 is provided with an air inlet 5 fortaking the air into the aqueous solution storage section 2. Further, thereaction section 1 is connected to an anode chamber 6, which is anegative electrode chamber of a fuel cell, by a hydrogen supply pipe 7,and hydrogen is supplied from the reaction section 1 to the anodechamber 6. The fuel cell is a polymer electrolyte fuel cell, and has astructure in which hydrogen supplied to the anode chamber 6 is notreleased to the outside.

Control over the supply of the aqueous malic acid solution to thereaction section 1, and over the stoppage of its supply is exercisedbased on FIG. 1. As a set hydrogen pressure for actuating the fuel cell,the internal pressure of the anode chamber 6 was set at atmosphericpressure. This is because the solid polymer membrane sandwiched betweenthe anode and the cathode is subjected to atmospheric pressure from thecathode side, and is also subject to the internal pressure of the anodechamber 6 from the anode side, so that the pressure difference betweenboth pressures is decreased to keep the stress on the solid polymermembrane low. The reference pressure is a value obtained by adding apressure, which is lost by the hydrogen supply pipe 7, to the sethydrogen pressure. In the present embodiment, however, the hydrogensupply pipe 7 is sufficiently thick and short. Thus, no pressure lossoccurs, and the reference pressure is atmospheric pressure equal to theset hydrogen pressure.

The aqueous solution storage section 2 is always under atmosphericpressure because of the air flowing in through the air inlet 5. Thevalve opening pressure of the check valve 4 is nearly equal to 0 Pa, andno pressure loss occurs during the passage of the aqueous malic acidsolution through the connecting pipe 3. Thus, the supply of the aqueousmalic acid solution, and the stoppage of its supply are determined bythe difference between the internal pressure of the reaction section 1and atmospheric pressure. Control over the supply of the aqueous malicacid solution, and the stoppage of the supply is exercised as in theprocess flow chart shown in FIG. 1, and its details will be offeredbelow.

The first step S1 is the step of performing the following actions: Uponhydrogen consumption associated with the power generation of the fuelcell, the internal pressure of the anode chamber 6 and the internalpressure of the reaction section 1 are lowered. If the internal pressureof the reaction section 1 is lower than atmospheric pressure, a force inthe liquid feed direction acts on the valve body of the check valve 4under the differential pressure between the reaction section 1 and theaqueous solution storage section 2, with the result that the check valve4 opens to supply the aqueous malic acid solution to the reactionsection 1.

The second step S2 is the step of causing a hydrogen generationreaction. When the aqueous malic acid solution is supplied to thereaction section 1, sodium borohydride and the aqueous malic acidsolution are brought into contact, whereby the sodium borohydridedissolves in the aqueous malic acid solution. In the aqueous malic acidsolution, the sodium borohydride associates with water, which is thesolvent, to cause a hydrogen generation reaction. On this occasion,dissolved malic acid works as a catalyst in a homogeneous system,showing the action of accelerating the reaction between sodiumborohydride and water.

The third step S3 is a step of the following mechanism: When theinternal pressure of the reaction section 1 exceeds atmospheric pressurebecause of hydrogen generation, a force in a direction opposite to theliquid feeding direction acts on the valve body of the check valve 4under the differential pressure between the reaction section 1 and theaqueous solution storage section 2 to close the check valve 4, therebystopping the supply of the aqueous malic acid solution.

By repeating the above-described steps, hydrogen can be supplied to theanode chamber 6, and hydrogen in an amount conformed to the outputcurrent of the fuel cell can be supplied. Since the check valve 4 isopened and closed in accordance with the pressure to feed the aqueousmalic acid solution, no electric power is required for liquid feedcontrol.

During stoppage of power generation by the fuel cell, there is nohydrogen consumption, and the reaction section 1 is kept at a constantpressure. Thus, the aqueous malic acid solution is not supplied to thereaction section 1, and fresh hydrogen does not occur anymore. That is,the supply of hydrogen can be stopped simultaneously with the stoppageof operation of the fuel cell.

FIG. 3 is a graph showing changes in the internal pressure of thehydrogen supply instrument and changes over time in the output voltageof the fuel cell when the hydrogen supply instrument and the fuel cellwere operated using the hydrogen generator according to the presentinvention. The concentration of the aqueous malic acid solution was setat 25% by weight, and a silicone-based anti-foaming agent wasincorporated. The ratio of water in the aqueous malic acid solution tosodium borohydride was set at 1.3.

The graph of FIG. 3 shows that a drop in the internal pressure of thereaction section 1 due to power generation of the fuel cell, and a risein the internal pressure of the reaction section 1 due to the hydrogengeneration reaction occurred repeatedly. Thus, the method of hydrogengeneration by the hydrogen generator of the present invention wasconfirmed. It was also found that the voltage of the fuel cell at thistime was constant, and a necessary amount of hydrogen was supplied fromthe hydrogen supply instrument.

The amount of supply of the aqueous malic acid solution was set in thefollowing manner: An end portion of the connecting pipe 3 on the side ofthe reaction section 1 was a nozzle having an inner diameter of theorder of 100 μm. The aqueous malic acid solution was supplied such thatafter forming droplets at the leading end of the nozzle, the aqueousmalic acid solution was added dropwise to sodium borohydride, wherebythe amount of supply of the aqueous malic acid solution per feeding wasset at 0.02 g. A rise in the pressure within the hydrogen supplyinstrument due to a hydrogen pressure calculated stoichiometrically fromthe above amount of supply was 30 kPa. The fuel cell had the cathodeopened to the atmosphere for oxygen diffusion and supply due to naturalconvection. The ambient temperature was 25° C., and the temperatureregulation of the cell was not performed. Power generation was carriedout, with the output power being fixed at 1 W.

As a result of the operation by this system, sodium borohydrideconverted into hydrogen by the time when the operation was completed was87% based on the entire sodium borohydride, and the hydrogen storagedensity at this time was 4.8% by weight.

As shown in FIG. 3, it is seen that within the system, the operation wasperformed at a pressure within a constant range, because owing to powergeneration, the internal pressure of the system lowered, but the supplyof the aqueous malic acid solution resulted in a rise in the pressure.The range of the changes in the pressure was from −5 kPaG to +10 kPaG,and the fluctuations in the output voltage due to these changes were assmall as several mV. Here, the reference pressure was 0 kPaG, but thepressure lowered to a value of the order of −5 kPa. This is because ittakes time for droplets to be formed at the leading end of the nozzlebefore the aqueous malic acid solution is added dropwise onto sodiumborohydride, and during this period, the pressure decreases. Thepressure increase calculated from the amount of a single supply of theaqueous malic acid solution is 30 kPa, but the upper limit of thepressure was nearly 10 kPa for the same reasons as mentioned above.

The method of setting the reaction conditions in FIG. 3, and the reasonfor setting these conditions will be described based on FIGS. 4 to 6.

FIG. 4 gives a graph showing the malic acid concentration dependence ofthe reaction efficiency when sodium borohydride was dissolved in anaqueous solution of malic acid.

As shown in FIG. 4, the ratio of water in the aqueous malic acidsolution with respect to sodium borohydride was 3. This measurement wasmade not by the method of the present invention in which an aqueousmalic acid solution is supplied, little by little, to sodiumborohydride, but by a method in which the amount of hydrogen generatedwhen dissolving all the reactants in a pressure vessel is calculatedfrom the internal pressure of the pressure vessel. The reactionefficiency exceeded 10% even when malic acid was incorporated at aconcentration of 0.1% by weight resulting in pH 3. At a malic acidconcentration of 25% by weight or higher, the reaction efficiencyreached saturation of about 85%. Even at a malic acid concentration of0.1% by weight, an effective hydrogen storage density was obtained.However, when the malic acid concentration was 25% by weight, thehydrogen storage density was found to peak. Thus, a malic acidconcentration of 25% by weight was selected as a condition.

FIG. 5 shows a graph showing the sodium borohydride concentrationdependence of the reaction efficiency. The malic acid concentration inthis measurement was 25% by weight. This measurement was made by thesame method as that which set the malic acid concentration in FIG. 3.

As shown in FIG. 5, the reaction efficiency was as high as 95% when theconcentration of sodium borohydride was low. However, as the sodiumborohydride concentration increased, the efficiency decreased. When thesodium borohydride concentration was 30% by weight, namely, when theratio of water in the aqueous malic acid solution to sodium borohydridewas 1.3, the hydrogen storage density with respect to the total weightof the reactants, calculated from the amount of hydrogen release, wasmaximal at 4.4% by weight. The reaction efficiency at this time was 81%.Thus, the ratio of water in the aqueous malic acid solution to sodiumborohydride being 1.3, and the malic acid concentration of 25% by weightwere found to be conditions presenting a maximum hydrogen storagedensity with the present system. Thus, these conditions were selected.

FIG. 6 is a graph showing the dependence of the reaction efficiency onthe pH of the malic acid concentration.

As shown in FIG. 6, the reaction efficiency was higher than 80%, whenthe pH was lower than 2. However, at too low a pH, the reaction occurredtoo rapidly. Thus, and for the purpose of maintaining a hydrogendensity, pH of 1 or above was found to be optimal. Preferably, a pH of1.4 or higher was found to be optimal.

When the pH exceeded 3, the reaction efficiency became 30% or lower, andthe hydrogen density also decreased. When the pH became lower than 1.4,or exceeded 2, the reaction efficiency and the hydrogen density tendedto decrease. In view of these findings, the pH of the malic acidconcentration can be said to be optimally 1 or higher, but 3 or lower.Preferably, and more optimally, the pH of the malic acid concentrationis 1.4 or higher, but 2 or lower.

As explained above, in the system utilizing the hydrogen generationreaction of sodium borohydride, it was found that it was possible tosupply hydrogen conformed to the electric current of the fuel cellwithout use of electric power and control the hydrogen generationreaction, and that the hydrogen storage density was increased.

FIG. 7 is a table showing, in addition to the above results of theexperiments, the use of other aqueous accelerator solutions, andcombinations when a solid accelerator was accommodated in the reactionsection 1, as well as the reaction efficiencies.

(1): The fuel cell was operated under conditions in which an aqueoussolution of 25% by weight of malic acid was used as an aqueousaccelerator solution containing 7.8 g of the accelerator with respect to10 g of sodium borohydride. The reaction efficiency was 87%. When theaqueous malic acid solution was used, hydrogen was obtained with a highdegree of conversion, and the pH of the aqueous solution containing theproduct was as low as 9.5.

(2): The fuel cell was operated under conditions where an aqueoussolution of 10% by weight of nickel chloride was used as an aqueousaccelerator solution containing 2.6 g of the accelerator with respect to10 g of sodium borohydride. The reaction efficiency was 91%. When theaqueous nickel chloride solution was used, the amount of the catalystwas reduced, and the degree of conversion could be rendered high.

(3): The fuel cell was operated under conditions where an aqueoussolution of 15% by weight of malic acid and 5% by weight of nickelchloride was used as an aqueous accelerator solution containing 5.3 g ofthe accelerator with respect to 10 g of sodium borohydride. The reactionefficiency was 94%. When the aqueous solution of malic acid and nickelchloride was used, the degree of conversion was rendered high, theamount of the catalyst could be reduced, and the pH of the aqueoussolution containing the product was of the order of 10.0.

(4): An aqueous solution of 10% by weight of nickel chloride was used asan aqueous accelerator solution, and 0.3 of solid nickel chloride wasaccommodated as a solid accelerator into the reaction section 1. Thefuel cell was operated, with the amount of the accelerator in theaqueous accelerator solution being 2.6 g with respect to 10 g of sodiumborohydride. When sodium borohydride was dissolved in the aqueousaccelerator solution to cause a hydrogen generation reaction, a rapidreaction rate was exhibited initially, but the reaction slowed overtime. The reaction site at a slow reaction rate was an aqueous solution.When this aqueous solution contacted the solid nickel chloride, thephenomenon was observed that the solid nickel chloride dissolved toincrease the rate of the hydrogen generation reaction. As a result, incomparison with the case where no solid nickel chloride was accommodatedin the reaction section, a long time was taken until the internalpressure of the reaction section 1 became lower than the referencepressure, and a large amount of water contained in the aqueousaccelerator solution was reacted. The reaction efficiency was 96%.

(5): In place of the solid nickel chloride in (4), 0.3 g of solid cobaltchloride was accommodated in the reaction section. The reactionefficiency was 96%.

(6): In place of the solid nickel chloride in (4), 0.5 g of solid malicacid was accommodated in the reaction section. The reaction efficiencywas 94%.

In (4) to (6), the catalyst was fixed in the reactor. Thus, the amountof the catalyst increased, but the degree of conversion could beenhanced.

(7): Instead of the aqueous solution of 10% by weight of nickel chloridein (6), an aqueous malic acid solution with a concentration of 20% byweight was used as the aqueous accelerator solution. The fuel cell wasoperated, with the amount of the accelerator in the aqueous acceleratorsolution being 5.8 g with respect to 10 of sodium borohydride. Thereaction efficiency was 91%.

(8): In place of the solid malic acid in (7) 0.3 g of solid cobaltchloride was accommodated in the reaction section. The reactionefficiency was 92%.

(9): In place of the solid cobalt chloride in (8), 0.3 g of palladiumwas accommodated as a precious metal into the reaction section. Thereaction efficiency was 89%.

In (7) to (9), the amount of the catalyst can be decreased, and thedegree of conversion can be raised. Moreover, the speed of fluctuationsin the internal pressure can be rendered low (see FIG. 9 to be describedlater), resulting in high safety and controllability.

(10): In addition to (3), 0.3 g of solid nickel chloride wasaccommodated as a solid accelerator into the reaction section 1. Thereaction efficiency was 97%.

In (10), the amount of the catalyst increased, because the catalyst wasfixed within the reactor. However, the degree of conversion can beraised.

Hence, the use of the combinations in (1) to (10) is found to exhibitvery high reaction efficiencies and obtain high hydrogen storagedensities.

Sodium, potassium and lithium can be used for salts of the metalchlorides, and iron can be used as the metal. Moreover, an aluminumhydride salt can be used as the complex hydride. When a metal consideredto be lower in oxidation-reduction potential than hydrogen is used forthe complex hydride, an acid is used as the accelerator of the aqueousaccelerator solution. Hydrochloric acid and sulfuric acid can be used asthe acid. For the complex hydride, an amphoteric metal can be used. Inthis case, a basic aqueous solution is used as the aqueous acceleratorsolution. Aluminum, zinc, tin, and lead are used as the amphotericmetals, and sodium hydroxide is used for the basic aqueous solution.

As described above, the aqueous solution of nickel chloride as a metalchloride is applied as the accelerator of the aqueous acceleratorsolution in (2), (4) to (6). Here, the concentration of nickel chlorideis 0.1% by weight or more, but 40% by weight or less, preferably 0.1% byweight or more to up to 25% by weight. Using FIG. 8, the dependence ofthe degree of conversion on the concentration of nickel chloride will beexplained.

FIG. 8 is a graph showing the dependence of the reaction efficiency onthe concentration of nickel chloride. In evaluating the reactionefficiency and the hydrogen density, the lower limit of theconcentration of nickel chloride was based on the degree of conversionin the initial stage of the reaction after a lapse of 5 minutes from theinitiation of the reaction, while the upper limit of the concentrationof nickel chloride was based on the height of the reaction efficiency oncompletion of the reaction. In the drawing, the values of the reactionefficiency and the hydrogen density at the left end on the ordinate axisare not values in the absence of nickel chloride, but values in % byweight upon addition of nickel chloride, for example, values of 0.1% byweight or less.

As shown in FIG. 8, a reaction efficiency of 10% or more was reached ina concentration region of 0.1% by weight or higher 5 minutes afterinitiation of the reaction, showing that the reaction proceeded with ahigh degree of conversion. In the concentration range of up to 20% byweight, a high reaction efficiency and a high hydrogen density wereobtained. In the concentration range of up to 25% by weight, theseparameters remained high. At the concentration exceeding 40% by weight,the reaction efficiency and the hydrogen density were kept in a nearlyunchanged state. Thus, a nickel chloride concentration, i.e., a metalchloride concentration, of 0.1% by weight or higher, but 40% by weightor lower, and further 0.1% by weight or higher, but 25% by weight orlower, was selected as a condition providing optimal values. Morepreferably, a metal chloride concentration of 1.0% by weight or higher,but 15% by weight or lower, is selected, because it is seen, as shown inFIG. 8, that between 1.0% by weight and 15% by weight, the reactionefficiency and the hydrogen density peak.

Based on FIGS. 9 and 10, an explanation will be offered for the reactionstatus prevailing when a fixed catalyst (a precious metal or a hydrogenabsorbing alloy) was accommodated in a reactor. FIG. 9 shows changesover time in the pressure of hydrogen generated (rate of hydrogengeneration) when the solid catalyst was not accommodated. FIG. 10 showschanges over time in the pressure of hydrogen generated (rate ofhydrogen generation) when the solid catalyst was accommodated. As theconcrete conditions, a current of 6 A was generated in (1) shown in FIG.7 in the case of FIG. 9, and a current of 6 A was generated in (7) shownin FIG. 7 in the case of FIG. 10.

FIG. 9 and FIG. 10 are different in the reaction rate when the aqueouscatalyst solution was added dropwise to sodium borohydride in the fuelcell system. Here, the slope of the graph is related to the rate ofhydrogen generation and the generated current. Since the generatedcurrent is equal in FIGS. 9 and 10, the difference in the profile isascribed to the difference in the rate of hydrogen generation. The rateof hydrogen generation is related to the amount of the catalyst and theamount of water supplied, and becomes higher as the amount of supplyincreases. Thus, when the aqueous accelerator solution is supplied, thegraph rises. One cycle of the profile is related to the amount of watersupplied, changes in the rate of hydrogen generation, and electriccurrent. The larger the amount of water supply, the longer the onecycle. Moreover, the shorter the time from the supply of the aqueousaccelerator solution until the rate of hydrogen generation changes andbecomes lower than the rate of hydrogen consumption due to currentgeneration, the shorter the one cycle becomes.

Both drawings will be compared below. The symbols (a) to (c) representthe contents of the corresponding cases.

FIG. 9

(a) The sodium borohydride and the aqueous solution meet each other toproceed with the reaction. Thus, the reaction rate changes smoothly.Consequently, the line of the graph shows few small irregularities.

(b) The rise and the fall are steep. This shows that the rate ofhydrogen generation changes to a high degree.

(c) One cycle is short, and the amount of water supply is small.

FIG. 10

(a) In addition to the meeting between the sodium borohydride and theaqueous solution, the materials during the reaction and the acceleratorfixed to the reactor contact each other to proceed with the reaction.The materials during the reaction are foamy, and contain sodiumborohydride and water on the surfaces of the foams. Since the materialsduring the reaction are in foamy shape, the timing of contact betweenthe accelerator fixed to the reactor and the materials during thereaction varies widely. Thus, there are many small irregularities on theline of the graph.

(b) The rise and the fall are gentle. This shows that the rate ofhydrogen generation changes slowly. Thus, high safety andcontrollability are obtained. The reasons why the rise speed slows arethat (i) since the accelerator is located within the reactor, the amountof contact between water and sodium borohydride is reduced at a timewhen the aqueous accelerator solution is supplied to sodium borohydride;and (ii) the concentration of the aqueous accelerator solution is low.

(c) One cycle is long, but the amount of the pressure change iscomparable to that in FIG. 9. The amount of water supply is large. Thereason is a slow rise speed.

FIG. 9 and FIG. 10 are different in pressure, because the valve openingpressure of the valve is different. The absolute values of the pressureare unrelated to the rate of hydrogen generation and the generatedcurrent.

That is, even when the aqueous accelerator solution and the sodiumborohydride are mixed, it is not that all the reactants reactimmediately. Thus, the outcome is the formation of a mixed aqueoussolution having the reactants mixed with the product already formed.This aqueous solution contains sodium borohydride, thus causing ahydrogen generation reaction. The reaction rate is slowed compared withthat immediately after supply of the aqueous accelerator solution. Thus,the reaction rate can be increased by contact with a solid acceleratorheld in solid form.

When the solid accelerator is accommodated, therefore, the speed offluctuations in the internal pressure can be lowered, ensuring highsafety and controllability. Even if the amount of water supplied isincreased, the amount of the pressure change is comparable. Thus, evenwhen no solid accelerator is accommodated, the amount of the pressurechange may be decreased by reducing the amount of water supply.Consequently, high safety and controllability are obtained.

The concrete configurations of a hydrogen generator and a fuel cellapparatus according to the present invention will be described based onFIGS. 11 to 22. In the drawings, the workpiece is described as a complexhydride, for example, sodium borohydride. The reaction solution isdescribed as an aqueous accelerator solution, for example, an aqueoussolution of malic acid. It is possible to apply a complex hydride, otherthan sodium borohydride, as the workpiece. It is also possible to apply,for example, the aqueous accelerator solution illustrated in FIG. 7 asthe reaction solution.

FIG. 11 shows the schematic configuration of a hydrogen generatoraccording to a first embodiment of the present invention. FIG. 12 showsthe schematic configuration of a hydrogen generator according to asecond embodiment of the present invention. FIG. 13 shows the schematicconfiguration of a hydrogen generator according to a third embodiment ofthe present invention.

The hydrogen generator according to the first embodiment will bedescribed based on FIG. 11.

A hydrogen generator 11 is equipped with a reaction chamber 12(corresponding to the reaction section 1 in FIG. 1) as a hydrogen supplyinstrument, and a workpiece 13 (e.g., sodium borohydride) as a hydrogengeneration reactant is stored in the reaction chamber 12. A solutiontank 15 as an aqueous solution reservoir is connected to the reactionchamber 12 via a liquid feed pipe 14 as a supply pipe. The liquid feedpipe 14 is connected to a liquid chamber 16 which is a fluid chamber ofthe solution tank 15. A reaction solution 17 (e.g., an aqueous solutionof malic acid), which is an aqueous accelerator solution, is stored inthe liquid chamber 16, and the liquid chamber 16 is partitioned by amoving wall 18.

The moving wall 18 is urged toward the liquid chamber 16 by acompression spring 19, and the liquid chamber 16 is pressed by themoving wall 18, and is thus pressurized. That is, the moving wall 18 isalways pressed by the compression spring 19. Thus, under conditionswhere the reaction solution 17 flows through the liquid feed pipe 14,the moving wall 18 can push out the reaction solution 17. When thereaction solution 17 is sent to the reaction chamber 12 through theliquid feed pipe 14, the reaction solution 17 and the workpiece 13contact to cause a hydrogen generation reaction. In the drawing, thenumeral 20 denotes an air inlet intended not to impede the movement ofthe moving wall 18.

A hydrogen conduit 21 as a discharge means is connected to the reactionchamber 12, and a regulator 22 is provided in the hydrogen conduit 21.The amount of hydrogen discharge from the reaction chamber 12 isregulated by the regulator 22. Although it is designed that the amountof hydrogen discharge can be controlled by the regulator 22, it ispossible to discharge hydrogen at a constant hydrogen pressure with theuse of a constant pressure valve.

A pressure regulating valve 23 for pressure regulation is installed inthe liquid feed pipe 14, and the pressure regulating valve 23 is a valvefor regulating the pressure when the reaction solution 17 is allowed toflow. The output pressure when the reaction solution 17 is allowed toflow is the pressure during opening of the pressure regulating valve 23(valve opening pressure). When the pressure inside the reaction chamber12 exceeds the valve opening pressure, the pressure regulating valve 23closes. When the pressure inside the reaction chamber 12 becomes lowerthan the valve opening pressure (falls to a predetermined value orlower), the pressure regulating valve 23 opens.

That is, the internal pressure of the liquid chamber 16 is kept at avalue higher than the pressure for opening of the pressure regulatingvalve 23 (is kept at a pressure adapted to open the pressure regulatingvalve 23 and exceeding the predetermined pressure value of the reactionchamber 12) as a result of pressurization. The pressure regulating valve23 is designed such that in a constant pressure state where the internalpressure of the reaction chamber 12 falls to the predetermined value orlower, the valve body opens to permit the passage of the reactionsolution 17 from the liquid chamber 16 to the reaction chamber 12.

The pressure regulating valve 23 is, for example, a constant pressurevalve, and is composed of a primary channel which is a channel on theside of the liquid chamber 16 of the solution tank 15, a secondarychannel which is a channel on the side of the reaction chamber 12, thevalve body provided between the primary channel and the secondarychannel, an external pressure transmission path for transmitting thepressure of the outside to the valve, and an internal pressuretransmission path for transmitting the internal pressure of the reactionchamber 12 to the valve body.

The solution tank 15 and the reaction chamber 12 may be constituted by asingle container member by separating the liquid chamber 16 of thesolution tank 15 from the reaction chamber 12 by a wall member as thepartition. Further, a communication hole may be formed in the wallmember separating the liquid chamber 16 and the reaction chamber 12, andthe pressure regulating valve 23 may be provided in the communicationhole. This configuration obviates the need for the liquid feed pipe 14,and can cut down the number of the components.

The actions of the above-described hydrogen generator 11 will bedescribed.

The reaction solution 17 is fed from the liquid chamber 16 of thesolution tank 15 to the reaction chamber 12 through the liquid feed pipe14. In addition to the pressurization of the liquid chamber 16, theinternal pressure of the reaction chamber 12 in the absence of hydrogengeneration is rendered so low as to open the pressure regulating valve23. Thus, the reaction solution 17 is fed through the liquid feed pipe14.

Upon feeding of the reaction solution 17 to the reaction chamber 12, thereaction solution 17 and the workpiece 13 contact and react to generatehydrogen. Once hydrogen is generated, the internal pressure of thereaction chamber 12 rises, and exceeds the valve opening pressure of thepressure regulating valve 23 (brings the pressure regulating valve 23 toclosure). Upon elevation of the internal pressure of the reactionchamber 12, the pressure regulating valve 23 enters into a closed stateto stop the supply of the reaction solution 17 through the liquid feedpipe 14.

When the reaction solution 17 is not supplied any more, the reactionrate of the hydrogen generation reaction in the reaction chamber 12lowers, and generated hydrogen is discharged through the hydrogenconduit 21 of the reaction chamber 12. Since the internal pressure ofthe reaction chamber 12 lowers, it becomes such a low pressure that thepressure regulating valve 23 is opened. As a result, the reactionsolution 17 is fed again from the liquid chamber 16 of the solution tank15 to the reaction chamber 12, whereby the reaction solution 17 and theworkpiece 13 contact to generate hydrogen.

Here, a pressing means is used to feed the reaction solution 17 from theliquid chamber 16 of the solution tank 15. That is, the moving wall 18is urged toward the liquid chamber 16 by the compression spring 19, andthe reaction solution 17 is fed under the pressurizing force with whichthe liquid chamber 16 is pressed by the moving wall 18. The reactionsolution 17 is always subject to the force, with which it is dischargedfrom the solution tank 15, by pressurization by means of the compressionspring 19 via the moving wall 18. However, the pressure changesaccording to the amount of displacement of the compression spring 19.

In connection with the change in the discharge speed of the reactionsolution 17, there is the pressure regulating valve 23 which is openowing to a decrease in the internal pressure of the reaction solution17, and whose valve opening pressure is constant. Thus, the dischargespeed of the reaction solution 17 is constant, regardless of thepressure of the liquid chamber 16 of the solution tank 15. Furthermore,the pressure regulating valve 23 is opened and closed depending on therelationship between the internal pressure and the external pressure ofthe reaction chamber 12. Since the external pressure (concretely,atmospheric pressure) is constant, the internal pressure of the reactionchamber 12 is kept nearly constant.

Hence, the reaction solution 17 can be stably supplied to the reactionchamber 12 in accordance with the pressure state without use of power,whereby hydrogen can be generated. By varying the capacity of the liquidchamber 16 by the moving wall 18, the liquid chamber 16 is pressurized,whereby the pressure state permitting the pressure regulating valve 23to open can be retained. Moreover, the moving wall 18 is pressed by theurging force of the compression spring 19. Thus, a very simpleconfiguration enables the moving wall 18 to be pressed.

The hydrogen generator according to the second embodiment will bedescribed based on FIG. 12. The same members as those shown in FIG. 11are assigned the same numerals as in FIG. 11, and duplicate explanationsare omitted.

A hydrogen generator 24 according to the second embodiment is arrangedto have a pair of magnets 25 instead of the compression spring 19 of thehydrogen generator 11 shown in FIG. 11. That is, a moving wall 18 isurged toward a liquid chamber 16 by the repulsive force of the magnets25, so that the liquid chamber 16 is pressed by the moving wall 18, andis thus pressurized. The moving wall 18 is always pressed by therepulsive force of the magnets 25. Thus, under conditions where areaction solution 17 flows through a liquid feed pipe 14, the movingwall 18 can push out the reaction solution 17.

With the hydrogen generator 24, therefore, the moving wall 18 can bepressed by a very simple configuration under the magnetic force of themagnets 25.

The hydrogen generator according to the third embodiment will bedescribed based of FIG. 13. The same members as those shown in FIGS. 11and 12 are assigned the same numerals as in FIGS. 11 and 12.

A hydrogen generator 28 is equipped with a reaction chamber 12, and aworkpiece 13 is stored in the reaction chamber 12. A solution tank 15 isconnected to the reaction chamber 12 via a liquid feed pipe 14, and theliquid feed pipe 14 is connected to a liquid chamber 16 of the solutiontank 15. A reaction solution 17 is stored in the liquid chamber 16. Ahydrogen conduit 21 is connected to the reaction chamber 12, and aregulator 22 is provided in the hydrogen conduit 21. The amount ofhydrogen discharge from the reaction chamber 12 is regulated by theregulator 22.

A pressure regulating valve 23 for pressure regulation is installed inthe liquid feed pipe 14, and the pressure regulating valve 23 is a valvefor regulating the pressure when the reaction solution 17 is allowed toflow. The output pressure when the reaction solution 17 is allowed toflow is the pressure during opening of the pressure regulating valve 23(valve opening pressure). When the pressure inside the reaction chamber12 exceeds the valve opening pressure, the pressure regulating valve 23closes. When the pressure inside the reaction chamber 12 becomes lowerthan the valve opening pressure (falls to a predetermined value orlower), the pressure regulating valve 23 opens.

Aside from the liquid feed pipe 14, a pressure transmission pipe 26connects the reaction chamber 12 to the liquid chamber 16 of thesolution tank 15. Hydrogen generated in the reaction chamber 12 is sentto the liquid chamber 16 of the solution tank 15 through the pressuretransmission pipe 26. A check valve 27 is provided in the pressuretransmission pipe 26, and the check valve 27 permits the passage ofhydrogen from the reaction chamber 12 only to the liquid chamber 16.That is, hydrogen is prevented from flowing from the liquid chamber 16to the reaction chamber 12.

The principle of supplying the reaction solution 17 to the reactionchamber 12 is based on the pressure difference between the solution tank15 and the reaction chamber 12 which has resulted from an increase inthe internal pressure of the solution tank 15 and a decrease in thepressure of the reaction chamber 12. Hydrogen is generated in thereaction chamber 12 to raise the pressure, whereby hydrogen flows fromthe reaction chamber 12 into the solution tank 15 to raise the internalpressure of the solution tank 15. In the reaction chamber 12, on theother hand, hydrogen is discharged to the outside through the hydrogenconduit 21 via the regulator 22, with the result that the pressure ofthe reaction chamber 12 decreases. Thus, a pressure difference arisesbetween the solution tank 15 and the reaction chamber 12, whereupon thereaction solution 17 moves toward the reaction chamber 12.

The actions of the above-described hydrogen generator 28 will bedescribed.

The reaction solution 17 is fed from the liquid chamber 16 of thesolution tank 15 to the reaction chamber 12 through the liquid feed pipe14. In addition to the pressurization of the liquid chamber 16, theinternal pressure of the reaction chamber 12 in the absence of hydrogengeneration is rendered so low as to open the pressure regulating valve23. Thus, the reaction solution 17 is fed through the liquid feed pipe14.

Upon feeding of the reaction solution 17 to the reaction chamber 12, thereaction solution 17 and the workpiece 13 contact and react to generatehydrogen. Once hydrogen is generated, the internal pressure of thereaction chamber 12 rises, and exceeds the valve opening pressure of thepressure regulating valve 23 (brings the pressure regulating valve 23 toclosure). Upon elevation of the internal pressure of the reactionchamber 12, the pressure regulating valve 23 enters into a closed stateto stop the supply of the reaction solution 17 through the liquid feedpipe 14.

When the reaction solution 17 is not supplied any more, the reactionrate of the hydrogen generation reaction in the reaction chamber 12lowers, and generated hydrogen is discharged through the hydrogenconduit 21 of the reaction chamber 12. Since the internal pressure ofthe reaction chamber 12 lowers, it becomes such a low pressure that thepressure regulating valve 23 is opened. As a result, the reactionsolution 17 is fed again from the liquid chamber 16 of the solution tank15 to the reaction chamber 12, whereby the reaction solution 17 and theworkpiece 13 contact to generate hydrogen.

Here, a pressing means is used to feed the reaction solution 17 from theliquid chamber 16 of the solution tank 15. That is, when hydrogen isgenerated within the reaction chamber 12 to raise the pressure, hydrogenis sent to the solution tank 15 through the pressure transmission pipe26 to transmit the pressure from the reaction chamber 12 to the solutiontank 15. Simultaneously, hydrogen in the reaction chamber 12 isdischarged through the hydrogen conduit 21, whereupon the internalpressure of the reaction chamber 12 lowers. As a result, the solutiontank 15 is pressurized by the action of the check valve 27 into a statewhere the internal pressure of the solution tank 15 is kept higher thanthe internal pressure of the reaction chamber 12. Thus, the reactionsolution 17 is fed to the reaction chamber 12.

Hence, the reaction solution 17 can be stably supplied to the reactionchamber 12 in accordance with the pressure state without use of power,whereby hydrogen can be generated. Moreover, the solution tank 15 ispressurized by hydrogen flowing in via the check valve 27 of thepressure transmission pipe 26, whereby a pressure state permitting thepressure regulating valve 23 to open can be retained.

The fuel cell apparatus equipped with the hydrogen generator of thepresent invention will be described based on FIGS. 14 and 15.

FIG. 14 shows the schematic configuration of the fuel cell apparatusaccording to the first embodiment of the present invention. FIG. 15shows the schematic configuration of the fuel cell apparatus accordingto the second embodiment of the present invention.

A fuel cell system 31 shown in FIG. 14 is a system in which the hydrogengenerator 11 shown in FIG. 11 is connected to a fuel cell 32. That is,the fuel cell 32 is equipped with an anode chamber 33 as a negativeelectrode chamber, and the anode chamber 33 constitutes a spacecontiguous to an anode room of a fuel cell unit cell 34. The anode roomis a space for temporarily storing hydrogen to be consumed by the anode.The anode chamber 33 and the reaction chamber 12 are connected by ahydrogen conduit 21, and hydrogen generated in the reaction chamber 12is supplied to the anode room of the anode chamber 33. Hydrogen suppliedto the anode room is consumed by the fuel cell reaction in the anode.The amount of hydrogen consumption in the anode is determined by theoutput current of the fuel cell 32.

The regulator 22 provided in the hydrogen conduit 21 shown in FIG. 11 isnot mounted, because it need not be installed.

The above-mentioned fuel cell system 31 can be configured as the fuelcell system 31 equipped with the hydrogen generator 11 which can stablysupply the reaction solution 17 and generate hydrogen without using acomplicated mechanism or mechanical power.

A fuel cell apparatus 35 shown in FIG. 15 is a system in which thehydrogen generator 28 shown in FIG. 13 is connected to a fuel cell 32.That is, the fuel cell 32 is equipped with an anode chamber 33, and theanode chamber 33 constitutes a space contiguous to an anode room of afuel cell unit cell 34. The anode room is a space for temporarilyholding hydrogen to be consumed by the anode. The anode chamber 33 andthe reaction chamber 12 are connected by a hydrogen conduit 21, andhydrogen generated in the reaction chamber 12 is supplied to the anoderoom of the anode chamber 33. Hydrogen supplied to the anode room isconsumed by the fuel cell reaction of the anode. The amount of hydrogenconsumption in the anode is determined by the output current of the fuelcell 32.

The regulator 22 provided in the hydrogen conduit 21 shown in FIG. 13 isnot mounted, because it need not be installed.

The above-mentioned fuel cell apparatus 35 can be configured as the fuelcell apparatus 35 equipped with the hydrogen generator 24 which canstably supply the reaction solution 17 and generate hydrogen withoutusing a complicated mechanism or mechanical power.

FIG. 16 shows the schematic configuration of a hydrogen generatoraccording to a fourth embodiment of the present invention. FIG. 17 showsthe schematic configuration of a hydrogen generator according to a fifthembodiment of the present invention. FIG. 18 shows the schematicconfiguration of a hydrogen generator according to a sixth embodiment ofthe present invention.

The hydrogen generator according to the fourth embodiment will bedescribed based on FIG. 16.

A hydrogen generator 41 is equipped with a reaction chamber 42, and aworkpiece 43 is stored in the reaction chamber 42. A solution container44 is provided inside the reaction chamber 42, and a reaction solution51, which is a reaction fluid, is stored in the solution container 44.The reaction chamber 42 and the solution container 44 are connected by aliquid feed pipe 45 as a fluid supply path. The liquid feed pipe 45connects the reaction chamber 42 and the solution container 44 togetherby way of the outside of the reaction chamber 42.

The solution container 44 comprises a bag member formed, for example, ofpolypropylene (flexible material: a film or a sheet-shaped material ofresin or rubber), and has a weighting plate 46 as a plate materialprovided at the bottom thereof. A compression spring 47 is providedbetween the weighting plate 46 and the bottom wall of the reactionchamber 42, and the weighting plate 46 is urged by the compressionspring 47. As the solution container 44, a flexible material, such asPET, silicone, silicone rubber, butyl rubber, or isoprene rubber, can beapplied in addition to polypropylene.

The solution container 44 is always pressed via the compression spring47 and the weighting plate 46. Thus, under conditions where the reactionsolution 51 flows through the liquid feed pipe 45, the reaction solution51 can be pushed out of the solution container 44. When the reactionsolution 51 is pushed out, the bag member is deformed, and the volume ofthe solution container 44 is decreased, because the solution container44 is pressed via the weighting plate 46. Thus, the capacity of thereaction chamber 42 is increased correspondingly. When the reactionsolution 51 is sent to the reaction chamber 42 through the liquid feedpipe 45, the reaction solution 51 and the workpiece 43 contact to causea hydrogen generation reaction in the reaction chamber 42 whose capacityhas increased.

A hydrogen conduit 50 is connected to the reaction chamber 42, and aregulator 52 is provided in the hydrogen conduit 50. The amount ofhydrogen discharge from the reaction chamber 42 is regulated by theregulator 52. Although it is designed that the amount of hydrogendischarge can be controlled by the regulator 52, it is possible todischarge hydrogen at a constant hydrogen pressure with the use of aconstant pressure valve.

A pressure regulating valve 53 for pressure regulation is installed inthe liquid feed pipe 45 at a site outside of the reaction chamber 42,and the pressure regulating valve 53 is a valve for regulating thepressure when the reaction solution 51 is allowed to flow. The outputpressure when the reaction solution 51 is allowed to flow is thepressure during opening of the pressure regulating valve 53 (valveopening pressure). When the pressure inside the reaction chamber 42exceeds the valve opening pressure, the pressure regulating valve 53closes. When the pressure inside the reaction chamber 42 becomes lowerthan the valve opening pressure (falls to a predetermined value orlower), the pressure regulating valve 13 opens.

That is, the internal pressure of the solution container 44 is kept at avalue higher than the pressure for opening of the pressure regulatingvalve 53 (is kept at a pressure adapted to open the pressure regulatingvalve 53 and exceeding the predetermined pressure value of the reactionchamber 42) as a result of pressurization. The pressure regulating valve53 is designed such that in a constant pressure state where the internalpressure of the reaction chamber 42 falls to the predetermined value orlower, the valve body opens to permit the passage of the reactionsolution 51 from the solution container 44 to the reaction chamber 42.

The pressure regulating valve 53 is, for example, a constant pressurevalve, and is composed of a primary channel which is a channel on theside of the solution container 44, a secondary channel which is achannel on the side of the reaction chamber 42, the valve body providedbetween the primary channel and the secondary channel, an externalpressure transmission path for transmitting the pressure of the outsideto the valve, and an internal pressure transmission path fortransmitting the internal pressure of the reaction chamber 42 to thevalve body.

As noted above, the reaction chamber 42 and the solution container 44are connected by the liquid feed pipe 45 by way of the outside of thereaction chamber 42. However, the liquid feed pipe 45 can be disposedinside the reaction chamber 42. Moreover, a check valve can be providedin a nozzle portion of the liquid feed pipe 45 opening into the reactionchamber 42. By providing the check valve, backflow of hydrogen generatedin the reaction chamber 42, or foams engulfing such hydrogen can beprevented. This decreases limitations on the posture of the hydrogengenerator 41 when in use.

The actions of the above-described hydrogen generator 41 will bedescribed.

The reaction solution 51 is fed from the solution container 44 to thereaction chamber 42 through the liquid feed pipe 45. In addition to thepressurization of the solution container 44, the internal pressure ofthe reaction chamber 42 in the absence of hydrogen generation isrendered so low as to open the pressure regulating valve 53. Thus, thereaction solution 51 is fed through the liquid feed pipe 45.

Upon feeding of the reaction solution 51 to the reaction chamber 42, thereaction solution 51 and the workpiece 43 contact and react to generatehydrogen. Once hydrogen is generated, the internal pressure of thereaction chamber 42 rises, and exceeds the valve opening pressure of thepressure regulating valve 53 (brings the pressure regulating valve 53 toclosure). Upon elevation of the internal pressure of the reactionchamber 42, the pressure regulating valve 53 enters into a closed stateto stop the supply of the reaction solution 51 through the liquid feedpipe 45.

When the reaction solution 51 is not supplied any more, the reactionrate of the hydrogen generation reaction in the reaction chamber 42lowers, and generated hydrogen is discharged through the hydrogenconduit 50 of the reaction chamber 42. Since the internal pressure ofthe reaction chamber 42 lowers, it becomes such a low pressure that thepressure regulating valve 53 is opened. As a result, the reactionsolution 51 is fed again from the solution container 44 to the reactionchamber 42, whereby the reaction solution 51 and the workpiece 43contact to generate hydrogen.

Here, a pressing means is used to feed the reaction solution 51 from thesolution container 44. That is, the weighting plate 46 is urged by thecompression spring 47 to deform the bag member into a state where thevolume of the solution container 44 is decreased. At the same time, thereaction solution 51 is pressurized, and fed by the pressing force. Thereaction solution 51 is always subject to the force, with which it isdischarged from the solution container 44, by pressurization resultingfrom the deformation (volume decrease) of the solution container 44 bymeans of the compression spring 47 via the weighting plate 46. However,the pressure changes according to the amount of displacement of thecompression spring 47.

In connection with the change in the discharge speed of the reactionsolution 51, there is the pressure regulating valve 53 which is openowing to a decrease in the internal pressure of the reaction solution51, and whose valve opening pressure is constant. Thus, the dischargespeed of the reaction solution 51 is constant, regardless of thepressure of the solution container 44. Furthermore, the pressureregulating valve 53 is opened and closed depending on the relationshipbetween the internal pressure and the external pressure of the reactionchamber 42. Since the external pressure (concretely, atmosphericpressure) is constant, the internal pressure of the reaction chamber 42is kept nearly constant.

Hence, the reaction solution 51 can be stably supplied to the reactionchamber 42 in accordance with the pressure state without use of power,whereby hydrogen can be generated. By urging the weighting plate 46 tovary the volume of the solution container 44, the solution container 44is pressurized, whereby a pressure state permitting the pressureregulating valve 53 to open can be retained. Moreover, the weightingplate 46 is pressed by the urging force of the compression spring 47.Thus, a very simple configuration enables the weighting plate 46 to bepressed.

As the reaction solution 51 of the solution container 44 is supplied tothe workpiece 43 of the reaction chamber 42, the weighting plate 46 ispressed by the urging force of the compression spring 47 to decrease thevolume of the solution container 44. Thus, the capacity of the reactionchamber 42 can be increased by an amount corresponding to the decreasein the volume of the solution container 44. Hence, a dead space iseliminated, so that the region of hydrogen generation can be increaseddespite a small space, making space saving possible without reducing theamount of hydrogen generation. Furthermore, the amount of hydrogengeneration can be increased without an increase in space.

Consequently, the above-described hydrogen generator 41 enables asufficient amount of hydrogen to be generated with a small volume.

The hydrogen generator according to the fifth embodiment will bedescribed based on FIG. 17. The same members as those shown in FIG. 16are assigned the same numerals as in FIG. 16, and duplicate explanationsare omitted.

A hydrogen generator 55 according to the fifth embodiment is equippedwith a solution container 56, as a fluid chamber, within a reactionchamber 42, instead of the solution container 44 shown in FIG. 16. Areaction solution 51 (for example, an aqueous solution of malic acid) isstored in the solution container 56. The reaction chamber 42 and thesolution container 56 are connected by a liquid feed pipe 45 as a fluidsupply path. The liquid feed pipe 45 connects the reaction chamber 42and the solution container 56 together by way of the outside of thereaction chamber 42.

The solution container 56 is composed of a bellows comprising a bellowsmember as a deformation allowing member, and comprises, for example,SUS, phosphor bronze, or beryllium. A weighting plate 57 as a platematerial is provided at the bottom of the solution container 56 (endportion of the bellows member). A compression spring 47 is providedbetween the weighting plate 57 and the bottom wall of the reactionchamber 42, and the weighting plate 57 is urged by the compressionspring 47. By pressing the solution container 56 via the weighting plate57, the bellows shrinks to decrease the volume of the solution container56.

The solution container 56 is always pressed via the compression spring47 and the weighting plate 57. Thus, under conditions where the reactionsolution 51 flows through the liquid feed pipe 45, the reaction solution51 can be pushed out of the solution container 56. When the reactionsolution 51 is pushed out, the bellows shrinks, and the volume of thesolution container 56 decreases, because the solution container 56 ispressed via the weighting plate 57. Thus, the capacity of the reactionchamber 42 is increased correspondingly. When the reaction solution 51is sent to the reaction chamber 42 through the liquid feed pipe 45, thereaction solution 51 and the workpiece 43 contact to cause a hydrogengeneration reaction in the reaction chamber 42 whose capacity hasincreased.

Hence, the reaction solution 51 can be stably supplied to the reactionchamber 42 in accordance with the pressure state without use of power,whereby hydrogen can be generated. By urging the weighting plate 57 tocontract the bellows, thereby varying the volume of the solutioncontainer 56, the solution container 56 is pressurized, whereby apressure state permitting the pressure regulating valve 53 to open canbe retained. As the reaction solution 51 of the solution container 56 issupplied to the workpiece 43 of the reaction chamber 42, the weightingplate 57 is pressed by the urging force of the compression spring 47 tocontract the bellows, thereby decreasing the volume of the solutioncontainer 56. Thus, the capacity of the reaction chamber 42 can beincreased by an amount corresponding to the decrease in the volume ofthe solution container 56. Hence, a dead space is eliminated, so thatthe region of hydrogen generation can be increased within a small space,making space saving possible without reducing the amount of hydrogengeneration. Furthermore, the amount of hydrogen generation can beincreased without an increase in space.

Consequently, the above-described hydrogen generator 55 enables asufficient amount of hydrogen to be generated with a small volume.

The hydrogen generator according to the sixth embodiment will bedescribed based on FIG. 18. The same members as those shown in FIGS. 16and 17 are assigned the same numerals as in FIGS. 16 and 17, andduplicate explanations are omitted.

A hydrogen generator 61 according to the sixth embodiment is equippedwith a solution container 62, as a fluid chamber, within a reactionchamber 42, instead of the solution container 44 shown in FIG. 16. Areaction solution 51 (for example, an aqueous solution of malic acid) isstored in the solution container 62. The reaction chamber 42 and thesolution container 62 are connected by a liquid feed pipe 45 as a fluidsupply path. The liquid feed pipe 45 connects the reaction chamber 42and the solution container 62 together by way of the outside of thereaction chamber 42.

The solution container 62 is composed of a cylinder 63 having an endportion (lower end portion) opened, and a piston plate 64 movablyprovided on the open end side of the cylinder 63 (a so-called syringestructure). The capacity of a cylinder chamber 65 is rendered variableby the movement of the piston plate 64, and the reaction solution 51 isstored in the cylinder chamber 65. A compression spring 47 is providedbetween the piston plate 64 and the bottom wall of the reaction chamber42, and the piston plate 64 is urged by the compression spring 47. Bypressing the piston plate 64, the capacity of the cylinder chamber 65 ofthe cylinder 63 is decreased to increase the open volume of the solutioncontainer 62 and decrease the volume of the solution container 62.

The piston plate 64 of the solution container 62 is always pressed viathe compression spring 47. Thus, under conditions where the reactionsolution 51 flows through the liquid feed pipe 45, the reaction solution51 can be pushed out of the cylinder chamber 65 of the solutioncontainer 62. When the reaction solution 51 is pushed out, the capacityof the cylinder chamber 65 decreases and the volume of the solutioncontainer 62 decreases, because the cylinder chamber 65 is pressed bythe piston plate 64. Thus, the capacity of the reaction chamber 42 isincreased correspondingly. When the reaction solution 51 is sent to thereaction chamber 42 through the liquid feed pipe 45, the reactionsolution 51 and the workpiece 43 contact to cause a hydrogen generationreaction in the reaction chamber 42 whose capacity has increased.

Hence, the reaction solution 51 can be stably supplied to the reactionchamber 42 in accordance with the pressure state without use of power,whereby hydrogen can be generated. By urging the piston plate 64 todecrease the capacity of the cylinder chamber 65 and vary the volume ofthe solution container 62, the solution container 62 is pressurized,whereby a pressure state permitting the pressure regulating valve 53 toopen can be retained.

As the reaction solution 51 of the solution container 62 is supplied tothe workpiece 43 of the reaction chamber 42, the piston plate 64 ispressed by the urging force of the compression spring 47 to decrease thecapacity of the cylinder chamber 65, thereby decreasing the volume ofthe solution container 62. Thus, the capacity of the reaction chamber 42can be increased by an amount corresponding to the decrease in thevolume of the solution container 62. Hence, a dead space is eliminated,so that the region of hydrogen generation can be increased within asmall space, making space saving possible without reducing the amount ofhydrogen generation. Furthermore, the amount of hydrogen generation canbe increased without an increase in space.

Consequently, the above-described hydrogen generator 61 enables asufficient amount of hydrogen to be generated with a small volume.

The fuel cell apparatus will be described based on FIGS. 19 to 21.

FIG. 19 shows the schematic configuration of a fuel cell apparatusaccording to a third embodiment of the present invention. FIG. 20 showsthe schematic configuration of a fuel cell apparatus according to afourth embodiment of the present invention. FIG. 21 show the schematicconfiguration of a fuel cell apparatus according to a fifth embodimentof the present invention. The same members as those shown in FIGS. 19 to20 are assigned the same numerals as in FIGS. 19 to 20, and duplicateexplanations are omitted.

A fuel cell apparatus 70 according to the third embodiment will bedescribed.

The fuel cell apparatus 70 shown in FIG. 19 is a system in which thehydrogen generator 41 shown in FIG. 16 is connected to a fuel cell 71.That is, the fuel cell 71 is equipped with an anode chamber 72, and theanode chamber 72 constitutes a space contiguous to an anode room of afuel cell unit cell 73. The anode room is a space for temporarilystoring hydrogen to be consumed by the anode.

The anode chamber 72 and the reaction chamber 42 are connected by ahydrogen conduit 50, and hydrogen generated in the reaction chamber 42is supplied to the anode room of the anode chamber 72. Hydrogen suppliedto the anode room is consumed by the fuel cell reaction in the anode.The amount of hydrogen consumption in the anode is determined by theoutput current of the fuel cell 71.

The regulator 52 provided in the hydrogen conduit 50 shown in FIG. 16 isnot mounted, because it need not be installed. Instead of the hydrogengenerator 41, it is possible to apply the hydrogen generator 55 shown inFIG. 17 or the hydrogen generator 61 shown in FIG. 18.

The above-mentioned fuel cell apparatus 70 can be configured as the fuelcell apparatus 70 equipped with the hydrogen generator 41 which cangenerate a sufficient amount of hydrogen with a small volume.

A fuel cell apparatus 81 according to the fourth embodiment will bedescribed.

The fuel cell apparatus 81 shown in FIG. 20 is composed of a hydrogengenerator 82 and a fuel cell 83. The hydrogen generator 82 and the fuelcell 83 are connected by a hydrogen conduit 84.

The hydrogen generator 82 will be described.

The hydrogen generator 82 is equipped with a reaction chamber 85 as areactant vessel, and a workpiece 86 (e.g., sodium borohydride) as ahydrogen generation reactant is stored in the reaction chamber 85. Asolution container 87 as a fluid chamber is provided inside the reactionchamber 85, and a reaction solution 88 (e.g., an aqueous solution ofmalic acid), which is a reaction fluid, is stored in the solutioncontainer 87.

A temporary reservoir is provided in the exterior of the reactionchamber 85, and the solution container 87 and the temporary reservoir 89are connected by a supply pipe 90. A pressure regulating valve 95 isprovided in the supply pipe 90, and when the pressure from the supplypipe 90 reaches a predetermined pressure or higher, the pressureregulating valve 95 opens to send the reaction solution 88 to thetemporary reservoir 89. In the drawing, the numeral 96 an air intakethrough which the air is taken in for the opening and closing actions ofthe pressure regulating valve 95.

A discharge pipe 91 opening into the reaction chamber 85 is connected tothe temporary reservoir 89, and a check valve 92 is provided in thedischarge pipe 91. By the action of the check valve 92, the reactionsolution 88 from the temporary reservoir 89 is allowed to pass throughthe discharge pipe 91, and the backflow of the reaction solution 88 fromthe reaction chamber 85 is prevented. When the reaction solution 88 isfed to the reaction chamber 85 through the discharge pipe 91, thereaction solution 88 and the workpiece 86 contact to cause a hydrogengeneration reaction in the reaction chamber 85.

The solution container 87 is a container as a bag-shaped membercomprising a flexible film (e.g., polypropylene). Upon feeding of thereaction solution 88 to the temporary reservoir 89, and uponpressurization by hydrogen generated in the reaction chamber 85, thevolume of the solution container 87 is decreased. That is, as thereaction solution 88 is supplied from the solution container 87 to thereaction chamber 85, the volume of the solution container 87 isdecreased, and the capacity of the reaction chamber 85 is increasedcorrespondingly.

The fuel cell 83 will be described.

The fuel cell 83 is equipped with an anode chamber 98, and the anodechamber 98 constitutes a space contiguous to an anode room of a fuelcell unit cell 99. The anode room is a space for temporarily holdinghydrogen to be consumed by the anode. The anode chamber 98 and thereaction chamber 85 are connected by a hydrogen conduit 84, and hydrogengenerated in the reaction chamber 85 is supplied to the anode room ofthe anode chamber 98. Hydrogen supplied to the anode room is consumed bythe fuel cell reaction in the anode. The amount of hydrogen consumptionin the anode is determined by the output current of the fuel cell 83.

The actions of the above-mentioned fuel cell apparatus 81 will bedescribed.

When the fuel cell unit cell 99 is connected to a load, hydrogen insidethe fuel cell apparatus 81 and oxygen in air cause a fuel cell reactionto generate electric power. Since power generation proceeds whileconsuming hydrogen, the internal pressure of the anode chamber 98, thehydrogen conduit 84, and the reaction chamber 85 falls. Here, thetemporary reservoir 89 is subjected to atmospheric pressure. If theinternal pressure becomes lower than atmospheric pressure, therefore, adifferential pressure arises between the temporary reservoir 89 and thereaction chamber 85. As a result, the reaction solution 88 (aqueousmalic acid solution) stored in the temporary reservoir 89 passes throughthe discharge pipe 91 and moves into the reaction chamber 85.

When the reaction solution 88 moves into the reaction chamber 85, thereaction solution 88 contacts the workpiece 86 (sodium borohydride) tocause a hydrogen generation reaction. Hydrogen generated passes throughthe hydrogen conduit 84, and is supplied to the anode chamber 98.Because of hydrogen generation, the internal pressure of the reactionchamber 85, the hydrogen conduit 84, and the anode chamber 98 exceedsatmospheric pressure, with the result that the internal pressure of thereaction chamber 85 becomes higher than the pressure of the temporaryreservoir 89. Thus, hydrogen is about to flow backward through thedischarge pipe 91, but this backflow is prevented by the check valve 92.

On the other hand, the solution container 87 is compressed under theinternal pressure of the reaction chamber 85, whereby the reactionsolution 88 stored within the solution container 87 is moved to thepressure regulating valve 95 through the supply pipe 90. The pressureregulating valve 95 is subjected to the pressure of the reactionsolution 88, for example, at 10 kPa (gauge pressure) in the valveclosing direction. When the internal pressure of the reaction chamber 85exceeds 10 kPa (gauge pressure), the force in the valve openingdirection surpasses the force in the valve closing direction under thepressure of the reaction solution 88. Thus, the pressure regulatingvalve 95 opens to supply the reaction solution 88 to the temporaryreservoir 89.

Then, the rate of hydrogen generation lowers, and the rate of hydrogenconsumption in the fuel cell 83 surpasses it, whereupon the internalpressure of the anode chamber 98, the hydrogen conduit 84, and thereaction chamber 85 begins to lower. While the internal pressure remainshigher than 10 kPa (gauge pressure), the pressure regulating valve 95 isopen, so that the reaction solution 88 flows from the temporaryreservoir 89 into the solution container 87. When the internal pressurebecomes lower than 10 kPa (gauge pressure) the pressure regulating valve95 is closed. The internal pressure of the temporary reservoir 89 atthis time is rendered 10 kPa (gauge pressure). If the internal pressureof the reaction chamber 85 further lowers, a pressure difference occursbetween the temporary reservoir 89 and the reaction chamber 85. As aresult, the check valve 92 opens, and the reaction solution 88 passesthrough the discharge pipe 91, moving to the reaction chamber 85. Thus,the reaction solution 88 contacts the workpiece 86 to cause a hydrogengeneration reaction, raising the internal pressure of the reactionchamber 85 again.

In accordance with the repetition of the above procedure, hydrogen isgenerated, and hydrogen as a fuel is supplied to the anode chamber 98 ofthe fuel cell 83.

As the reaction solution 88 is supplied from the solution container 87to the reaction chamber 85, the volume of the solution container 87 isdecreased, and the capacity of the reaction chamber 85 is increasedcorrespondingly. Hence, a dead space is eliminated, so that the regionof hydrogen generation can be increased within a small space, makingspace saving possible without reducing the amount of hydrogengeneration. Furthermore, the amount of hydrogen generation can beincreased without an increase in space.

The above-mentioned fuel cell apparatus 81 can be configured as the fuelcell apparatus 81 equipped with the hydrogen generator 82 which cangenerate a sufficient amount of hydrogen with a small volume.

A fuel cell apparatus 101 according to the fifth embodiment will bedescribed.

The fuel cell apparatus 101 shown in FIG. 21 is composed of a hydrogengenerator 102 and a fuel cell 83. The hydrogen generator 102 and thefuel cell 83 are connected by a hydrogen conduit 84.

The hydrogen generator 102 will be described.

The hydrogen generator 102 is equipped with a reaction chamber 85 as areactant vessel, and a workpiece 86 (e.g., sodium borohydride) as ahydrogen generation reactant is stored in the reaction chamber 85. Asolution container 87 as a fluid chamber is provided inside the reactionchamber 85, and a reaction solution 88 (e.g., an aqueous solution ofmalic acid), which is a reaction fluid, is stored in the solutioncontainer 87.

A temporary reservoir 89 is provided in the exterior of the reactionchamber 85, and the solution container 87 and the temporary reservoir 89are connected by a supply pipe 90. A check valve 103 is provided in thesupply pipe 90. By the action of the check valve 93, the reactionsolution 88 from the solution container 87 is allowed to pass throughthe supply pipe 90, and the backflow of the reaction solution 88 fromthe temporary reservoir 89 is prevented. The solution container 87 ispressurized by hydrogen generated in the reaction chamber 85, and whenthe pressure from the supply pipe 90 reaches the pressure of thetemporary reservoir 89 or higher, the reaction solution 88 is sent tothe temporary reservoir 89.

A discharge pipe 91 opening into the reaction chamber 85 is connected tothe temporary reservoir 89, and a pressure regulating valve 104 isprovided in the discharge pipe 91. When the internal pressure of thereaction chamber 85 falls to a predetermined pressure or lower, thepressure regulating valve 104 opens to enable the reaction solution 88from the temporary reservoir 89 to pass through the discharge pipe 91.The internal pressure of the temporary reservoir 89 is raised by thereaction solution 88 to be brought to a state higher than the pressureat which the pressure regulating valve opens (i.e., to a pressureexceeding the predetermined pressure value of the reaction chamber 85for permitting the pressure regulating valve 104 to open). In accordancewith the difference in internal pressure between the temporary reservoir89 and the reaction chamber 85, the reaction solution 88 is fed to thereaction chamber 85 through the discharge pipe 91. As a result, thereaction solution 88 and the workpiece 86 contact to cause a hydrogengeneration reaction in the reaction chamber 85.

The solution container 87 is a container as a bag-shaped membercomprising a flexible film (e.g., polypropylene). Upon feeding of thereaction solution 88 to the temporary reservoir 89, and uponpressurization by hydrogen generated in the reaction chamber 85, thevolume of the solution container 87 is decreased. That is, as thereaction solution 88 is supplied from the solution container 87 to thereaction chamber 85, the volume of the solution container 87 isdecreased, and the capacity of the reaction chamber 85 is increasedcorrespondingly.

The actions of the above-mentioned fuel cell apparatus 101 will bedescribed.

When the fuel cell unit cell 99 is connected to a load, hydrogen insidethe fuel cell 83 and oxygen in air cause a fuel cell reaction togenerate electric power. Since power generation proceeds while consuminghydrogen, the internal pressure of the anode chamber 98, the hydrogenconduit 84, and the reaction chamber 85 falls. Here, the temporaryreservoir 89 is subjected to atmospheric pressure. If the internalpressure becomes lower than atmospheric pressure, therefore, adifferential pressure arises between the temporary reservoir 89 and thereaction chamber 85. As a result, the reaction solution 88 (aqueousmalic acid solution) stored in the temporary reservoir 89 passes throughthe discharge pipe 91 and moves into the reaction chamber 85.

When the reaction solution 88 moves to the reaction chamber 85, thereaction solution 88 contacts the workpiece 86 (sodium borohydride) tocause a hydrogen generation reaction. Hydrogen generated passes throughthe hydrogen conduit 84, and is supplied to the anode chamber 98.Because of hydrogen generation, the internal pressure of the reactionchamber 85, the hydrogen conduit 84, and the anode chamber 98 exceedsatmospheric pressure, with the result that the internal pressure of thereaction chamber 85 becomes higher than the pressure of the temporaryreservoir 89. Thus, hydrogen is about to flow backward through thedischarge pipe 91, but this backflow is prevented by the pressureregulating valve 104.

On the other hand, the solution container 87 is compressed under theinternal pressure of the reaction chamber 85, whereby the reactionsolution 88 stored within the solution container 87 is passed throughthe supply pipe 90 and the check valve 103, and supplied to thetemporary reservoir 89.

Then, the rate of hydrogen generation lowers, and the rate of hydrogenconsumption in the fuel cell 83 surpasses the rate of hydrogengeneration, whereupon the internal pressure of the anode chamber 98, thehydrogen conduit 84, and the reaction chamber 85 begins to lower. Whenthe internal pressure lowers, and a pressure difference occurs betweenthe temporary reservoir 89 and the reaction chamber 85, the pressureregulating valve 104 opens to flow the reaction solution 88 from thetemporary reservoir 89 to the solution container 87. As a result, thereaction solution 88 contacts the workpiece 86 to cause a hydrogengeneration reaction, raising the internal pressure of the reactionchamber 85 again.

In accordance with the repetition of the above procedure, hydrogen isgenerated, and hydrogen as a fuel is supplied to the anode chamber 98 ofthe fuel cell 83.

As the reaction solution 88 is supplied from the solution container 87to the reaction chamber 85, the volume of the solution container 87 isdecreased, and the capacity of the reaction chamber 85 is increasedcorrespondingly. Hence, a dead space is eliminated, so that the regionof hydrogen generation can be increased within a small space, makingspace saving possible without reducing the amount of hydrogengeneration. Furthermore, the amount of hydrogen generation can beincreased without an increase in space.

The above-mentioned fuel cell apparatus 101 can be configured as thefuel cell apparatus 101 equipped with the hydrogen generator 102 whichcan generate a sufficient amount of hydrogen with a small volume.

According to the present embodiments, as described above, it is possibleto provide a method of hydrogen generation and a hydrogen generatorwhich permit uniform and efficient contact between the complex hydrideand the catalyst, can generate hydrogen at the required rate, and imparta high reaction efficiency and a high hydrogen storage density.

According to the present embodiments, moreover, it is possible toprovide a fuel cell apparatus equipped with a hydrogen generator whichpermits uniform and efficient contact between the complex hydride andthe catalyst, can generate hydrogen at the required rate, and imparts ahigh reaction efficiency and a high hydrogen storage density.

INDUSTRIAL APPLICABILITY

The present invention can be utilized, for example, in the industrialfield of hydrogen generators which decompose metal hydrides to generatehydrogen.

1. A fuel cell apparatus, comprising: a fuel cell having a negativeelectrode chamber, a positive electrode chamber and an electrolytedisposed between the negative and positive electrode chambers; and ahydrogen generator having a reaction chamber that contains a complexhydride capable of reacting with an aqueous reagent solution to generatehydrogen, and a storage chamber that contains an aqueous reagentsolution that is supplied to the reaction chamber to react with thecomplex hydride to generate hydrogen; wherein the reaction chamber isconnected by a hydrogen supply pipe to the negative electrode chamber tosupply hydrogen from the reaction chamber to the negative electrodechamber, and wherein a set hydrogen pressure of the fuel cell is notlower than the internal pressure of the positive electrode chamber, butis not higher than a pressure which is higher than the internal pressureof the positive electrode chamber by 0.3 MPa.
 2. A fuel cell apparatusaccording to claim 1; wherein the hydrogen generator includes a controldevice that controls the supplying of the aqueous reagent solution fromthe storage chamber to the reaction chamber based on a referencepressure such that the aqueous reagent solution is repeatedly suppliedto the reaction chamber when the reference pressure is greater than theinternal pressure within the reaction chamber and not supplied to thereaction chamber when the reference pressure is less than the internalpressure within the reaction chamber.
 3. A hydrogen generator accordingto claim 2; wherein the reference pressure is atmospheric pressure.
 4. Ahydrogen generator according to claim 2; wherein the control devicecomprises a check valve that is disposed in the supply pipe and thatopens and closes in response to a differential pressure between thestorage chamber and the reaction chamber, the check valve opening whenthe internal pressure within the reaction chamber becomes lower than thereference pressure to permit flow of the aqueous reagent solution to thereaction chamber and closing when the internal pressure within thereaction chamber becomes higher than the reference pressure to preventflow of the aqueous reagent solution to the reaction chamber.
 5. Ahydrogen generator according to claim 4; further including means forcontinually maintaining the aqueous reagent solution in the storagechamber under pressure.
 6. A hydrogen generator according to claim 2;wherein the control device comprises a pressure regulating valve that isdisposed in the supply pipe and that opens and closes in response to adifferential pressure between the storage chamber and the reactionchamber, the pressure regulating valve opening when the internalpressure within the reaction chamber becomes lower than the referencepressure to permit flow of the aqueous reagent solution to the reactionchamber and closing when the internal pressure within the reactionchamber becomes higher than the reference pressure to prevent flow ofthe aqueous reagent solution to the reaction chamber.
 7. A hydrogengenerator according to claim 6; further including means for continuallymaintaining the aqueous reagent solution in the storage chamber underpressure.